Pavlova O. The alterations of vascular smooth muscles contractile machinery Ca2+-sensitivity with protein kinase C blockade at different genesis vasospastic conditions (experimental study)

The aim of present study was to investigate the possibility of protein kinase C (PKC) participation in mechanisms of different vasospastic conditions development via its influences on vascular smooth muscle contractility properties. It is known that one of possible mechanism of vasospasm development is increasing of contractile machinery sensitivity to Са2+ in vascular smooth muscle cells (SMC). We investigate the alterations in PKC-mediated Са2+-sensitivity of contractile machinery in vascular SMC at models of different aetiology hypertensive and vasospastic conditions including pulmonary vasoconstriction elicited by hypoxic influence, genetically determinated hypertension, and hypertension elicited by action of whole body ionizing irradiation. Investigations were made on chemically permeabylized (skinned) isolated rat pulmonary artery and rat aorta segments. In b-escin skinned rat pulmonary artery segments hypoxia (pO2=10-20 mmHg) elicited shift in pCa-tension curve to the left that suggest about increasing of SMC myofilament Са2+-sensitivity. Application of chelerythrine (10-6 М) and staurosporine (10-7 M), the potent PKC inhibitors, at normoxic condition (pO2=135-145 mmHg) had no effect on Са2+-sensitivity of contractile machinery in rat pulmonary artery SMC. However, at hypoxic condition chelerythrine and staurosporine elicited shift of pCa-tension curve to value registries at normal oxygenation. Hypoxia elicited shift in pCa-tension curve to the right in b-escin skinned rat aorta segments that suggest about SMC myofilament Са2+-sensitivity decreasing. Chelerythrine (10-6 М) or staurosporine (10-7 M) application had no effect on pCa-tension curve neither at normoxic no at hypoxic conditions. In experiments on skinned segments of rat aorta taken from spontaneously hypertensive animals was observe shift in pCa-tension curve to the left compared with rat aorta of normotensive animals suggesting that SMC myofilament Са2+-sensitivity is increased. PKC inhibitors chelerythrine (10-6 М) and staurosporine (10-7 М) significantly increased the рСа50 value for pCa-tension relation. Similar results were obtained on rat aorta radiation treated animals (9th and 30th days after whole body exposure to radiation, dose 6 Gy, source Co60) where registers increasing of рСа50 to compared with rat aorta of control normotensive animals. The additions of chelerythrine (10-6 М) or staurosporine (10-7 М) in bath solution decrease the Са2+-sensitivity of contractile machinery in rat aorta SMC. To summarise, we have shown that contractile machinery Са2+-sensitivity of vascular SMC is increased at different vasospastic conditions via PKC activity increasing. We conclude that PKC-mediated increase of calcium sensitivity of contractile machinery in vascular SMC is one of the common mechanisms that can contribute to different genesis vasospastic conditions development. Our date also suggests that PKC inhibitors can normalised the hyperreactivity of vascular smooth muscle at hypertensions elicited by different reasons.